In assembling a pipeline, it is common to align the abutting ends of two pipe sections together with a line-up clamp positioned within the pipe sections at the joint to be welded. Once aligned, a more effective weld can be performed by use of back-up shoes, particularly made of copper, at the joint to be welded which engage the inside surface of both pipe sections at the joint. Devices such as shown in U.S. Pat. No. 5,356,067 to Leduc, U.S. Pat. No. 5,110,031 to Rinaldi, U.S. Pat. No. 4,556,162 to Gwin, et. al., and U.S. Pat. No. 3,937,382 to Cunningham, et. al., disclose devices with back-up shoes and discuss the advantages thereof.
Smaller diameter pipe cannot accept the typical line-up pipe clamp as discussed in the patents noted above. For smaller pipe, a technique has been developed, as disclosed in U.S. Pat. No. 5,090,608 to Jones, for providing a line-up clamp using expandable disks, made of polyurethane, to clamp against the inside surfaces of the pipe sections to be welded. In smaller pipe, no effective back-up shoe mechanism has yet been developed.